The performance of the coating depends on the raw materials used, among which the main film-forming substance, namely the binder, has the greatest effect. It is the main body of paint and the basis of paint, so it is also called base material or paint. The performance of the binder determines the basic performance of the coating. Different binders also have a great influence on the construction of coatings. Because of this, people often use different binders to distinguish and call the category names of coatings, such as epoxy resin coatings, asphalt coatings, alkyd resin coatings, silicone heat-resistant coatings, etc.
Film-forming substances for coatings, namely binders, can be divided into two categories: converting and non-converting.
One type is that the composition structure of the film-forming substance does not change during the film-forming process of the paint, that is, the composition and structure of the film-forming substance and the coating film are the same. This type is called a non-conversion film-forming substance. They are thermoplastic, softened by heat, and after cooling It becomes hard again, and most of them are soluble and meltable substances. These film-forming substances include natural resins, artificial synthetic resins, synthetic high molecular linear polymers, that is, thermoplastic resins (such as perchlorethylene resins) , polyvinyl acetate resin, etc.), chlorinated rubber, acrylic resin, etc.
The other type is that the composition structure of the film-forming substance changes during the film-forming process of the paint, and the film substance forms a coating film with a different composition and structure, which is called a conversion film-forming substance. They have functional groups that can react chemically, under the action of heat, oxygen or other substances, they can
Synthesize an insoluble and infusible network structure polymer that is different from the original composition structure, that is, a thermosetting polymer. Film-forming substances belonging to this category include drying oils and semi-drying oils derived from vegetable oils; natural lacquer and urushiol; adducts or reactants of low molecular compounds, such as adducts of polyisocarboxylates; Synthetic polymers, such as phenolic resins, alkyd resins, polyurethane prepolymers, acrylic oligomers, thermosetting acrylic resins, etc. In addition, there are a variety of new polymers, such as group transfer polymers, interpenetrating network polymers and so on.
The current coatings often use several types of resins to co-operate and modify each other to make the coating performance better and to meet various performance requirements.
